Function.prototype.myBind = function(obj){
  return (...args)=>{
    this.call(obj, ...args)
  }
}

let user = {
  age: 24
};

function func(para1, para2) {
  console.log([this.age, para1, para2]);
}

let method = func.myBind(user);
func('foo', 'bar') //undefined, foo, bar
method('foo', 'bar'); //24, foo, bar